1. Field of the Invention
The present invention relates generally to an antilock brake control system for motorcycles, and more particularly to an estimated vehicle speed detection apparatus for use in the antilock brake control system.
2. Description of the Prior Art
When the brakes are applied on a motorcycle in motion, the rotational velocity of the wheels decreases and the travel speed of the motorcycle therefore also decreases.
However, when the brakes are applied in such a manner that a stopping force greater than a certain threshold determined by the coefficient of friction of the road surface is created, such as when the brakes are applied suddenly in an emergency, the wheels lock and slip on the road surface, resulting in a dangerous situation. Antilock brake control systems are designed to eliminate this wheel locking condition by automatically reducing the braking force. One condition used to determine whether to start antilock brake control is a wheel speed slower by a predetermined amount than the vehicle speed, which is determined by comparing the wheel speed with the vehicle speed.
However, an estimated vehicle speed calculated according to the wheel speed is generally used for the vehicle speed. If the estimated vehicle speed is calculated based on the speed of a wheel which is currently under antilock brake control or is being braked, the difference between the actual vehicle speed and the estimated vehicle speed increases. As a result, it becomes difficult to accurately apply antilock brake control.